JP2018125254A - Manufacturing method of membrane electrode assembly for polymer electrolyte fuel cell - Google Patents

Abstract

A solid polymer fuel that is less likely to cause performance degradation due to flooding under high humidification conditions even when an alloy-based catalyst is used, and that is resistant to cracking of the coating film during application and drying of the catalyst ink. A method for producing a membrane electrode assembly for a battery is provided. An electrode catalyst layer 50 formed from a catalyst ink 3 and a solid polymer electrolyte membrane 10 are obtained by a method including a coating / drying step of forming an electrode catalyst layer 50 by applying and drying the catalyst ink 3 while heating. The membrane electrode assembly 18 for a polymer electrolyte fuel cell is manufactured. The catalyst ink 3 contains carbon particles carrying a catalyst, a polymer electrolyte, and a solvent, and the catalyst contains a binary catalyst containing an alloy of platinum and cobalt, or an alloy of platinum, cobalt, and manganese. It is a ternary catalyst. The mass ratio of the polymer electrolyte to the carbon particles in the catalyst ink 3 is in the range of 0.5 to 1.1. [Selection] Figure 1

Description

  The present invention relates to a method for producing a membrane electrode assembly for a polymer electrolyte fuel cell.

A polymer electrolyte fuel cell having a structure in which a polymer electrolyte membrane is sandwiched between a cathode electrode catalyst layer and an anode electrode catalyst layer operates at room temperature and has a short start-up time. Has been.
Conventionally, platinum is used as the catalyst metal in the catalyst layer. However, platinum is an expensive noble metal. Therefore, as a method for maintaining catalytic activity while reducing the amount of platinum used, an alloy of platinum and cobalt is used. Catalysts are known. In recent years, research on ternary catalysts as disclosed in Patent Document 1 and Patent Document 2 in which a third metal such as manganese is added to an alloy of platinum and cobalt has been actively conducted.

However, in the manufacturing process of the alloy-based catalyst, since acid treatment or the like is performed to stabilize the alloy, water is introduced at a location where a hydrophilic functional group is introduced into the carbon particles or the catalyst metal reaches out. Sometimes it was easy to accumulate. For this reason, when the fuel cell is operated under high humidification conditions, flooding in which water stays tends to occur, which causes a decrease in performance.
In the technique disclosed in Patent Document 3, a method of introducing a layer made of carbon nanofibers between a catalyst layer and a gas diffusion layer is performed as a countermeasure against flooding due to the above cause. However, this method has a problem that the number of processes and materials used is increased, and there is a possibility that the performance may be deteriorated when the thickness of the carbon nanofiber layer is not appropriate.

JP 2011-150867 A International Publication No. 2014/126077 JP 2008-276949 A

  In the present invention, even when an alloy catalyst is used, it is difficult to cause performance deterioration due to flooding under high humidification conditions, and the coated polymer film is not easily cracked during coating and drying of the catalyst ink, and has excellent durability. It aims at providing the manufacturing method of the membrane electrode assembly for fuel cells.

  A method for producing a membrane electrode assembly for a polymer electrolyte fuel cell according to an aspect of the present invention includes a method for producing a polymer electrolyte fuel cell in which an electrode catalyst layer formed from a catalyst ink and a polymer electrolyte membrane are joined. A method for producing a membrane electrode assembly, wherein the catalyst ink contains carbon particles carrying a catalyst, a polymer electrolyte, and a solvent, and the catalyst is a binary catalyst containing an alloy of platinum and cobalt, Alternatively, a ternary catalyst containing an alloy of platinum, cobalt, and manganese, the mass ratio of the polymer electrolyte to the carbon particles in the catalyst ink is in the range of 0.5 to 1.1, and the catalyst ink is heated. The gist of the present invention is to provide a coating and drying step of forming an electrode catalyst layer by coating and drying.

  According to the present invention, even when an alloy-based catalyst is used, performance deterioration due to flooding is unlikely to occur under high humidification conditions, and the coating film is not easily cracked during application and drying of the catalyst ink. A membrane electrode assembly for a molecular fuel cell can be produced.

It is the schematic explaining the manufacturing method of the membrane electrode assembly for polymer electrolyte fuel cells which concerns on 1st embodiment of this invention. It is the schematic explaining the manufacturing method of the membrane electrode assembly for polymer electrolyte fuel cells which concerns on 2nd embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings. The present embodiment is not limited to the embodiment described below, and modifications such as design changes based on the knowledge of those skilled in the art can be added, and such modifications have been added. The embodiment is also included in the scope of the present embodiment.
Also, in the following detailed description, specific details are set forth in order to provide a thorough understanding of embodiments of the invention. However, it will be apparent that one or more embodiments may be practiced without such specific details. In other instances, well-known structures and devices are shown in schematic form in order to simplify the drawing.

(Method for producing catalyst ink)
A method for producing the catalyst ink 3 for forming the electrode catalyst layer 50 of the polymer electrolyte fuel cell according to this embodiment will be described.
The catalyst ink 3 can be produced by mixing and dispersing carbon particles and a polymer electrolyte in a dispersion medium (solvent). The carbon particles carry a binary catalyst containing an alloy of platinum and cobalt, or a ternary catalyst containing an alloy of platinum, cobalt and manganese.

For mixing / dispersing, for example, a homogenizer, a planetary mixer, a dissolver, a bead mill or the like can be used. In the present embodiment, carbon black carrying an alloy catalyst is used as an example of carbon particles carrying a catalyst.
As the polymer electrolyte, a polymer material having proton conductivity, for example, a fluorine-based polymer electrolyte or a hydrocarbon-based polymer electrolyte is used.

  The dispersion medium is preferably selected from alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, and pentanol. Moreover, it is possible to use the solvent with which 2 or more types was mixed among the solvents mentioned above.

(Method for producing membrane electrode assembly)
FIG. 1 is a schematic view for explaining a method for producing a membrane electrode assembly for a polymer electrolyte fuel cell according to the first embodiment of the present invention. First, the transfer substrate 1 made of a polymer is loaded on the heating unit 20 of the heating device in a state where the surface is held smooth (FIG. 1A).
Next, the catalyst ink 3 is applied on the transfer substrate 1 with a coating device while being heated by the heating unit 20 (FIG. 1B), and dried to form the electrode catalyst layer 50 for the anode. Thus obtained substrate for transfer 1a with catalyst layer is obtained (FIG. 1 (c)). Further, in the same manner, a transfer substrate 1c with a catalyst layer on which the electrode catalyst layer 50 for cathode is formed is produced.

  The transfer substrate 1 is a sheet made of a material that can peel the electrode catalyst layer 50. For example, fluorine such as ethylene tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroperfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), etc. In addition to a resin, a polystyrene heat-resistant film or the like can be used.

  At this time, the mass ratio of the polymer electrolyte in the catalyst ink 3 to be applied and dried to the carbon particle carrier was set in the range of 0.5 to 1.1. If the mass ratio of the polymer electrolyte to the carbon particle carrier is too high, it causes a decrease in gas permeability and a decrease in power generation performance due to flooding. In particular, when an alloy catalyst is used, since the tendency to flood is strong, the mass ratio of the polymer electrolyte to the carbon particle carrier is preferably 1.0 or less.

On the other hand, if the mass ratio of the polymer electrolyte to the carbon particle carrier is too small, the strength of the coating film becomes weak in the coating and drying step of the catalyst ink 3 and causes cracking. This crack is a factor that causes a decrease in the durability of the fuel cell.
However, in the first embodiment of the present invention, since the catalyst ink 3 is applied to the transfer substrate 1 on the heating unit 20 of the heating device, the catalyst ink 3 can be applied and dried while being heated. As a result, the occurrence of cracks during application and drying of the catalyst ink 3 can be suppressed even under conditions where the mass ratio of the polymer electrolyte to the carbon particle carrier is low, specifically 0.5 or more. Therefore, it is possible to suppress a decrease in durability of the fuel cell due to cracks in the coating film of the catalyst ink 3.

The transfer substrates 1a and 1c with a catalyst layer produced as described above are placed opposite to each other with the electrode catalyst layer 50 facing the surface of the solid polymer electrolyte membrane 10 and subjected to heat and pressure by the thermal transfer device 30 ( FIG. 1 (d)). Thereby, the electrode catalyst layer 50 is transferred to both surfaces of the solid polymer electrolyte membrane 10 respectively.
By removing the transfer substrates 1a and 1c after the heat and pressure, a membrane electrode assembly 18 for a polymer electrolyte fuel cell in which the electrode catalyst layer 50 is bonded to both surfaces of the polymer electrolyte membrane 10 is obtained ( FIG. 1 (e)).

Furthermore, another embodiment of the present invention will be described. FIG. 2 is a schematic view for explaining a method for manufacturing a membrane electrode assembly for a polymer electrolyte fuel cell according to a second embodiment of the present invention.
First, the solid polymer electrolyte membrane 10 having the back sheet 11 on the back surface is loaded on the heating unit 20 of the heating device in a state where the surface is held smooth (FIG. 2A). Thereafter, while heating by the heating unit 20, the liquid catalyst ink 3 is applied to the surface of the solid polymer electrolyte membrane 10 by a coating device (FIG. 2B), and the heat in the heating unit 20 causes the catalyst ink 3 in the catalyst ink 3. Volatile components (such as a solvent) are removed to obtain the electrode catalyst layer 50 (FIG. 2 (c)).

Further, the back sheet 11 is peeled and removed from the solid polymer electrolyte membrane 10 (FIG. 2D), the solid polymer electrolyte membrane 10 is turned upside down, and the surface on which the electrode catalyst layer 50 is not formed faces upward. Then, it is loaded on the heating unit 20 with the surface held smooth (FIG. 2 (e)).
Next, while heating again with the heating unit 20, the liquid catalyst ink 3 is applied to the surface of the solid polymer electrolyte membrane 10 with a coating device (FIG. 2F), and the catalyst ink is heated by the heat of the heating unit 20. 3 is removed (FIG. 2 (g)) to obtain a membrane electrode assembly 18 for a polymer electrolyte fuel cell having the electrode catalyst layers 50 on both sides (FIG. 2 (h)).

  In the first embodiment, the catalyst ink 3 is applied to the surface of the transfer substrate 1 and dried to form the electrode catalyst layer 50, and the electrode catalyst layer 50 is formed on both surfaces of the solid polymer electrolyte membrane 10. In the second embodiment, the electrode catalyst layer 50 was formed by directly applying and drying the catalyst ink 3 on both surfaces of the solid polymer electrolyte membrane 10. However, the electrode catalyst layer 50 is transferred from the transfer substrate 1 to one surface of the solid polymer electrolyte membrane 10, and the catalyst ink 3 is directly applied to the other surface and dried to form the electrode catalyst layer 50. May be.

[Example]
Examples of the present invention and comparative examples will be described below.
Example 1
(Manufacture of catalyst ink)
A polymer electrolyte water dispersion was added to a carbon particle carrier supporting 45% by mass of platinum, 4% by mass of cobalt, and 1% by mass of manganese, and this was mixed and dispersed in 1-propanol. At this time, a bead mill was used for mixing and dispersing. At this time, the polymer electrolyte was prepared so that the mass ratio with respect to the mass of the carbon particle carrier was 0.6.

(Formation of electrode catalyst layer)
Next, a fluorine-based transfer substrate (Aflex (registered trademark) manufactured by Asahi Glass Co., Ltd., thickness 50 μm) in a state where high flatness is maintained is placed on the adsorption stage heated to 100 ° C., and the catalyst The ink was applied to the surface of the transfer substrate with a die coater. And it heated and dried for 5 minutes with the adsorption stage, and obtained the base material for transfer with a catalyst layer.

When forming the electrode catalyst layer for the cathode, the thickness of the electrode catalyst layer is adjusted so that the amount of platinum contained in the solid content is 0.4 mg / cm ² , and the electrode catalyst layer for the anode is formed. At that time, the thickness of the electrode catalyst layer was adjusted so that the amount of platinum contained in the solid content was 0.1 mg / cm ² . At this time, it was confirmed that there was no crack in the electrode catalyst layer. The surface of a fluorine-based solid polymer electrolyte membrane (Nafion (registered trademark) HP manufactured by Chemers Co., Ltd.) was sandwiched between the obtained transfer substrate with a catalyst layer and heat-pressed at 120 ° C. When sandwiching, the electrode catalyst layer of the transfer base material with the catalyst layer was arranged facing the surface of the fluorine-based solid polymer electrolyte membrane. After heat-pressing, only the transfer substrate was peeled from the fluorine-based solid polymer electrolyte membrane to obtain a membrane electrode assembly. As a result of evaluating the power generation performance of the obtained membrane / electrode assembly, it was confirmed that good power generation performance was obtained under both low and high humidification conditions.

(Example 2)
Example 1 except that a carbon particle carrier carrying 45% by mass of platinum and 5% by mass of cobalt is used, and that the mass ratio of the polymer electrolyte to the carbon particle carrier is 1.0. In the same manner as described above, a membrane electrode assembly of Example 2 was obtained. At this time, it was confirmed that there was no crack in the electrode catalyst layer. Moreover, as a result of evaluating the power generation performance of the obtained membrane electrode assembly, it was confirmed that good power generation performance was obtained under both the low and high humidification conditions.

(Comparative Example 1)
A membrane / electrode assembly of Comparative Example 1 was obtained in the same manner as in Example 1 except that the preparation was performed so that the mass ratio of the polymer electrolyte and the carbon particle carrier was 1.3. At this time, it was confirmed that there was no crack in the electrode catalyst layer. Moreover, as a result of evaluating the power generation performance of the obtained membrane electrode assembly, the performance deteriorated due to flooding under high humidification conditions.

(Comparative Example 2)
In the process of forming the membrane electrode assembly, the catalyst ink was applied not on the heated adsorption stage, but on the adsorption stage at room temperature, and after the application, except that it was dried in an oven at 80 ° C. for 5 minutes. As in Example 1, a membrane electrode assembly of Comparative Example 2 was obtained. At this time, cracks were generated in the electrode catalyst layer in the step of applying and drying the catalyst ink.

DESCRIPTION OF SYMBOLS 1 ... Transfer substrate 1a, 1c ... Transfer substrate with catalyst layer 3 ... Catalyst ink 10 ... Solid polymer electrolyte membrane 11 ... Back sheet 18 ... Solid polymer type Membrane electrode assembly for fuel cell 20 ... heating unit 30 ... thermal transfer device 50 ... electrode catalyst layer

Claims (3)

A method for producing a membrane electrode assembly for a polymer electrolyte fuel cell in which an electrode catalyst layer formed from a catalyst ink and a polymer electrolyte membrane are joined,
The catalyst ink contains carbon particles carrying a catalyst, a polymer electrolyte, and a solvent,
The catalyst is a binary catalyst containing an alloy of platinum and cobalt, or a ternary catalyst containing an alloy of platinum, cobalt and manganese,
The mass ratio of the polymer electrolyte to the carbon particles in the catalyst ink is in the range of 0.5 to 1.1.
A method for producing a membrane / electrode assembly for a polymer electrolyte fuel cell comprising a coating / drying step of forming the electrode catalyst layer by coating and drying the catalyst ink while heating.   2. The membrane electrode assembly for a polymer electrolyte fuel cell according to claim 1, wherein, in the coating and drying step, the catalyst ink is directly applied to the surface of the solid polymer electrolyte membrane and dried to form the electrode catalyst layer. 3. Production method.   In the coating and drying step, the catalyst ink is applied to the surface of the transfer substrate and dried to form the electrode catalyst layer, and the electrode catalyst layer on the transfer substrate is formed on the surface of the solid polymer electrolyte membrane. The method for producing a membrane electrode assembly for a polymer electrolyte fuel cell according to claim 1, wherein the membrane electrode assembly is transferred to the membrane.

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